Large stationary gas turbines with sequential combustion have been proven in industrial application. In these gas turbines, two combustion chambers are arranged in series in the flow direction, and each with an associated turbine which are exposed to admission of the hot gas which is produced in the respective combustion chamber. Gas turbines of this type, which for example are offered by the Assignee of the present invention under the type designation GT24/26, are described for example in the printed publication by Joos F. et al., “Field experience with the sequential combustion system of the GT24/26 gas turbine family”, ABB Review 5/1998, p. 12-20 (1998). FIG. 1 of which is reproduced in the present application as FIG. 1. A further description of such a gas turbine originates furthermore from EP-B1-0 620 362.
FIG. 1 shows a gas turbine 10 with sequential combustion, in which a compressor 11, a first combustion chamber 14, a high-pressure turbine 15, a second combustion chamber 17 and a low-pressure turbine 18 are arranged in series along an axis 19. In summary, these gas turbines can be described as follows: The compressor 11 and the two turbines 15 (HD), 18 (ND) are part of a rotor which rotates around the axis 19. The compressor 11 compresses the inducted air, wherein this compressed air then flows into a plenum and from there flows into the first combustion chamber. This combustion chamber is operated with premix burners, as originate for example from EP-A1-0 321 809, and furthermore from EP-A2-0 704 657. The compressed air flows into the premix burners whereintermixing with at least one fuel takes place. This fuel/air mixture then flows into the first combustion chamber 14, in which this mixture combusts, forming a stable flame front. The hot gas which thus results is partially expanded in the adjoining high-pressure turbine 15, performing work, and after that flows into the second combustion chamber 17 where a further fuel feed 16 takes place. As a result of the high temperatures, which the hot gas which is partially expanded in the high-pressure turbine 15 always has, combustion takes place in the second combustion chamber 17, which is based on spontaneous ignition. The hot gas which is reheated in the second combustion chamber 17 is then expanded in a multistage low-pressure turbine 18, in which blade rows of rotor blades and stator blades are arranged in series in an alternating manner.
In the known gas turbine of FIG. 1, the stator blades 20′ are formed as straight blades which are characterized by internal cooling. The trailing edge is cooled by means of the cooling medium which is used, in most cases by means of cooling air, wherein this cooling air is then blown out at least partially through holes which are drilled in the blade trailing edge. As a result of the straight shape of the stator blade and the cooling, which is matched to it, by means of an impingement cooling insert, limitations in efficiency result, however, the overcoming of which would bring advantages in the design of the gas turbine.